1. Field of the Invention
The present invention relates, in general, to a polypeptide. In particular, the present invention relates to an antagonist of vasoactive intestinal peptide.
2. Background Information
Vasoactive intestinal polypeptide (VIP) is a widely distributed peptide hormone which mediates a variety of physiological responses including gastrointestinal secretion, relaxation of gastrointestinal, vascular, and respiratory smooth muscle, lipolysis in adipocytes, pituitary hormone secretion, and excitation and hyperthermia after injection into the central nervous system (Snedecor and Cochran (1967) Statistical Methods pp. 508-509. Ames, Iowa: ISU Press; Said (1981) In: Gut Hormones, Bloom and Polak, eds., Ed. 2, pp. 379-384, New York: Churchhill-Livingston, Inc.). VIP is synthesized as a preprohormone composed of 170 amino acid residues (Cuttitta et al. (1988) J. Clin. Endo. Met. 67:576-583). VIP, a 28 amino acid peptide with an amidated C-terminal, results from posttranslational processing (Said & Mutt (1970) Science 69:1217-1218). The VIP peptide has been shown to contain at least two functional regions, a region involved in receptor specific binding and a region involved in biological activity (Gozes & Brenneman (1989) Molecular Neurobiology 3:201-236).
Another biological function of VIP is as a modulatory agent in the central nervous system (CNS) and periphery (Said & Mutt (1970) Science 69:1217-1218). In the rat brain, VIP elevates cAMP levels and stimulates adenylate cyclase in the cortex, striatum, hypothalmus, hippocampus, thalamus, and midbrain (Deschodt-Lanckman et al. (1977) FEBS Lett. 83:76-80; Etgen and Browning (1983) J. Neurosci. 3:2487-2493; Kerwin et al. (1980) J. Pharm. Pharmacol. 32:561-566; Quick et al. (1978) Biochem. Pharmacol. 27: 2209-2213). Further, VIP fulfills several criteria for a neurotransmitter mediating penile erection. It is present in nerve fibers innervating cavernous smooth muscle and blood vessels and is elevated during erection [Ottesen et al. (1984) Br. Med. J. 288:9; Dixon et al. (1984) J. Endocrinol. 100:249]. Injection of exogenous VIP induces erection in man (Ottesen et al. (1984) Br. Med. J. 288:9) and penile levels have been shown to be decreased in impotent men (Gu et al. (1984) Lancet 2:315). Since VIP appears to be important in erection formation (Anderson et al. (1984) J. Physiol. 350:209), its administration might help in relieving penile dysfunction.
VIP is also biologically active in the mammalian lung and has been found to be colocalized to cholinergic neurons in the lung (Shimosegawa et al. (1989) Reg. Peptides 2:181). Endogenous VIP is present in nerves supplying airway smooth muscle as well as glands and in pulmonary vessels within the normal adult lung (Ley et al. (1981) Cell Tissue Res. 220:238). VIP functions in the lung as a bronchodilator and relaxes pulmonary vascular smooth muscles (Diamond et al. (1983) Am. Rev. Respir. Dis. 128:827-832; Greenburg et al (1985) Thorax 40:715P; Morice et al.(1984) Lancet 1:457-458). Also, VIP is deficit in the airways of patients with bronchial asthma (Lebacq-Verheyden et al. (1988) J. Cell. Biochem. 36:85-96).
The actions caused by VIP may be mediated by specific receptors. VIP receptors were initially detected in the CNS using brain homogenates (Robberecht et al. (1978) Eur. J. Biochem. 90:147-154) and more recently autoradiographic studies have localized the receptors to discrete brain areas such as the cerebral cortex, striatum, supraoptic nucleus of the hypothalmous, dentate gyrus, pinneal and area postrema (Besson et al. (1984) Peptides 5:339-340; DeSouza et al. (1985) Neurosci. Lett. 56: 113-120; Shaffer and Moody (1986) Peptides 7:283-288). VIP receptors have also been characterized in liver membranes (Bataille et al. (1974) Endocrinology 95:713-721) and pancreatic acinar cells (Christophe et al. (1976) J. Biol. Chem. 251:4629-4634).
The biological actions of VIP in the lung may also be mediated by VIP receptors which have been detected in binding assays using plasma membranes derived from the rat, mouse, guinea pig, and human lung (Christophe et al. (1981) Peptides 2:253-258; Dickinson et al. (1986) Peptides 7:791-800; Robberecht et al. (1982) Peptides 4:241-250). Using in vitro autoradiographic techniques and lung slices, VIP receptors have been localized to the alveoli and epithelium of the rat lung and pulmonary artery smooth muscle and alveolar walls of the human lung (Leroux et al. (1984) Endocrinology 114:1506-1512; Leys et al. (1984) FEBS Lett. 199:198-202). The lung VIP receptors were characterized using cross-linking techniques and found to have an apparent molecular weight of 67 Kdaltons (Lebacq-Verheyden et al. (1988) Mol. Cell. Biol. 8:3129-3135). Additionally, it has been demonstrated that VIP positively regulates adenylate cyclase activity in the lung (Oilerenshaw et al. (1989) N. Engl. J. Med 320:1244-1248).
Recently, it was determined that VIP receptors are present in the malignant lung (Shaffer et al. (1987) Peptides 8:1101-1106). Lung cancer is a serious public health problem which kills approximately 150,000 people in the United States annually (Minna, J. D. et al (1985) in: Cancer: principles and practice of oncology (DeVita et al., eds.) pp. 507-599). Traditionally lung cancer is treated with chemo and/or radiation therapy but better survival rates might be possible with the development of new modes of therapy. Lung cancer can be divided into small cell lung cancer (SCLC) which accounts for approximately 25% of the lung cancer cases and non-small cell lung cancer (NSCLC). NSCLC can be further subdivided into adenocarcinoma, large cell carcinoma and squamous cell carcinoma each of which account for approximately 25% of the lung cancer cases. SCLC uses bombesin/gastrin releasing peptide (BN/GRP) as an autocrine growth factor (Cuttitta F. et al., (1985) Nature 316, 823-825). Thus SCLC synthesizes and secretes BN/GRP, and BN or GRP bind to cell surface receptors and stimulate the growth of SCLC. Further, NSCLC synthesizes and secretes transforming growth factor alpha (TGF-alpha), which binds to cell surface epidermal growth factor (EGF) receptors and stimulates NSCLC growth (Imanishi L. et al. (1989) J. NAtl. Cancer Inst. 81, 220-223). In contrast, VIP receptors are present in cells derived from SCLC and the three other major types of lung cancer (all members of NSCLC), large cell carcinoma, squamous cell carcinoma, and adenocarcinoma (Shaffer M. M. et al. (1987) Peptides 8, 1101-1106).
The present invention provides a novel VIP antagonist and methods of using same to alter the function of the vasoactive intestinal peptide. The invention further provides a method of inhibiting lung cancer using this antagonist.